file Frage Motor upgrade

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21 Nov 2018 10:10 #55192 von MagIO2
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I would say yes ... but ...

I also think that it should be enough to drive Y with 2 NEMA 17 steppers. And the solution to add another driver for the additional stepper is to enhance the parallel board. Use one side for forwarding the signals to the driver board and the other side to add the additional driver. On the parallel board you have access to all important signals.

Downside is, that it won't work with the WinPC NC USB-board.

SC 420 mit DIY parallel + Proxxon mit Mod + SprintLayout + LibreCAD->QCAD + WinPC starter/USB->EstlCAM/Arduino + DIY Shield + DIY Vakuumtisch

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21 Nov 2018 10:22 #55194 von skynet
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Definitely not. The driver is already under some strain just driving one motor. My board was brown under the Y axis motor from the heat. The driver is only good for 2A and each Y axis motor is 1.8A. Also the driver is current limited to 1.8A (resistor divider). If you hooked up two motors to one driver you would either blow the driver or end up with barely enough current to move them. Bad solution.
No need to do anything on the parallel board. I have made my own control unit with the extra driver, and now Stepcraft will release their own controller for the same purpose and it will work with both UCCNC and WinPC. Just hold on a bit longer and you can have that with warranty and everything.

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21 Nov 2018 11:24 #55196 von MagIO2
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I think you do not read careful enough ...

I don't say, that the one Y-stepper-driver-chip should drive 2 motors. I say that the space occupied by the parallel-board can be used to add another driver-chip listening to the same Y axis signals than the existing one (including Emergency-stop signal). Only thing which needs to be wired up there is a connection to the power-supply.

That said .. another solution would be to use the 4th axis-board space and add a stepper-driver-circuit there, which can handle both steppers. There you have power-supply and the room to add connectors. With the right software it's only a configuration-change. The old driver for Y can then be used as 4th axis driver, if needed.

DIY guys don't need warranty and everything, which basically means extra money ;o) And how long will this 'bit longer' be? A lot of old forum users already made their experience with SC announcements.

SC 420 mit DIY parallel + Proxxon mit Mod + SprintLayout + LibreCAD->QCAD + WinPC starter/USB->EstlCAM/Arduino + DIY Shield + DIY Vakuumtisch

Gruß, Andreas

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21 Nov 2018 11:30 #55197 von skynet
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Routing the lines for the parallel port and a driver in that space, not sure that's a good idea, and like you said, WinPC users would be out of luck.
The 4th axis space would be possible, even modifying the 4th axis board by setting the correct micro stepping, but that would not be a good solution for those who use the 4th axis. I'm a DIY guy and I made my own board, if you have the knowledge to add a driver to either the parallel board space or the 4th axis, you can also make a new control unit. No need for any sacrifices.

A bit longer they said was before the end of the year. Haven't heard from them in a few weeks, so I'm not sure what's the progress.

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21 Nov 2018 13:43 #55199 von MagIO2
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Well ... life is a big optimization process ... and different people have different optimization goals.

Some might not like the idea of replacing a board which is not broken, some might not like the idea to spend money (we will see how much the upgrade-kit costs in the end), some have the opinion that 2 NEMA 17 are enough boost for such a machine .... ( in case the 2 NEMA 23 hit the end of the machine, how will the spindle nuts react? SC might like the idea of selling spindle nuts abos ;o)

I am only throwing in some ideas and avoid to say things like "definitely not" or "no way" ...

For me the backlash of Y and X seem to be a bigger problem ... and I don't have any hope that SC will do anything for SC1 owners here.

SC 420 mit DIY parallel + Proxxon mit Mod + SprintLayout + LibreCAD->QCAD + WinPC starter/USB->EstlCAM/Arduino + DIY Shield + DIY Vakuumtisch

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21 Nov 2018 14:04 #55200 von skynet
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Nema 23 seems like an argument for different drivers all together. With the current output of the stepcraft control units being limited to 1.4A or 1.8A, I doubt you'd see enough gains from using Nema 23 with the same drivers...

My 840 is running fine with 2 Nema 17 on the Y axis. I know a guy from Finland who is running his with all Nema 23 motors in closed loop with a complete replacement of the electronics. So far it's working fine, but he had to limit the speed to way below the motor's capacity, or he might break it. And they look ridiculously big for the machine.
Do you mean the lead screw nuts when you say spindle nuts? Yeah, in the long run it might be more reasonable to use ball nuts with that kind of power...

Can't the new adjustable nuts be used on the SC1? I can't see it on the manual...

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21 Nov 2018 15:00 #55201 von MagIO2
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I thought you were mentioning the NEMA 23 steppers in the first place, but have mercy, I became 50 recently, so, too old to remember the details in the right context.

Adjustable nuts: "No way" ;o))

SC1 has an 8mm lead screw and lead screw nuts (SC calls them spindle nuts in their online shop). SC2 has 10mm ... and different slope as well. SC1 is more precise with 400 steps per mm vs. 300 steps per mm on SC2,

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21 Nov 2018 15:08 #55202 von skynet
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Oh ok, I don't know much about the SC1. I would guess between the steel screws and the brass nut, if anything wears out, it would be the nut, no? If so, just getting a replacement should be enough to bring the backlash to "new" or "almost new" condition.

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10 Feb 2019 00:17 #55927 von mayhem2408
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skynet schrieb: Answer is no. The good news is that since I published my mod, Stepcraft got in touch and they will release an upgrade pack with a new control unit and all the parts needed to have the two y-axis motors.

Did they give any indication on time? The Y axis is so under powered with the single stepper and would do the upgrade in a heart beat.

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10 Feb 2019 09:47 #55934 von peterg1000
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Sorry to disagree here - if the machine is properly adjusted there is adequate power in the standard motors. I can achieve slew rates of over 3000mm/min on all axes on my 420/2.

I actually measured the torque required to move the Y axis once adjusted, and found it to be less than 10% of the rated torque of the stepper.

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There is no problem, however simple, that cannot be made more complicated by thinking about it.

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10 Feb 2019 09:52 #55935 von skynet
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I'm still waiting for news. I don't have a date yet.

peterg1000, could be, but it makes it quite sensitive do get the "proper adjustment". While it might seem trivial to you, it seems like it isn't for most people. There's also a lot of people who will be very happy not to have to deal with the belt ever again.

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10 Feb 2019 11:09 - 10 Feb 2019 11:10 #55939 von mayhem2408
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peterg1000 schrieb: Sorry to disagree here - if the machine is properly adjusted there is adequate power in the standard motors. I can achieve slew rates of over 3000mm/min on all axes on my 420/2.

I actually measured the torque required to move the Y axis once adjusted, and found it to be less than 10% of the rated torque of the stepper.

I set the tension on the rails/roller to produce the recommended 1kg (10nm) required to move it.
The X axis rail on the 840 is twice the weight of that on the 420 so the Y axis is under more strain to get it to move, and stepper loose torque the faster they go.

The standard Y axis stepper can only pull its maximum torque up to 300RPM (900mm/min) and looses about 25% of its torque at 1000RPM (3000mm/min) and it rapidly drops off from there to the point it doesn't have enough torque to turn its own shaft.

Having two steppers on the Y axis will reduce the torque required by the motor and make it less likely to stall.
Last edit: 10 Feb 2019 11:10 by mayhem2408.

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10 Feb 2019 11:14 #55940 von mayhem2408
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skynet schrieb: I'm still waiting for news. I don't have a date yet.

peterg1000, could be, but it makes it quite sensitive do get the "proper adjustment". While it might seem trivial to you, it seems like it isn't for most people. There's also a lot of people who will be very happy not to have to deal with the belt ever again.


I second that. Get rid of the belt. I've already replaced it once and the replacement is starting to look a bit strained and need to be replaced again. Hopefully the dual stepper upgrade is available before this belt wears out.

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10 Feb 2019 12:59 #55941 von hasew
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Has anybody measured the stiffness of a D.840/v2? The spec states 0.1 - 0.14mm for a load of 20N. I can hardly believe this can be reached with stock steppers, since you have to put some tension on the rollers. Especially when X and Y are positioned in their axis' center positions. Furthermore, it seems the X extrusion is quite likely to twist under load.

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10 Feb 2019 21:04 #55948 von mayhem2408
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@hasew I do recall when assembling my X axis that I has to have a couple of attempts because the X axis rail which is over 600mm long it had twisted. The left side was perfect but the right side was causing ridges in the bottom of pocket cuts. By loosening the right side and giving it a light twist, it is OK now.

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